1 / 20

Supernova Explosions and Cosmic Ray Sources in Our Galaxy

Explore the relationship between supernova explosions and cosmic ray sources in our galaxy, with a focus on dwarf stars and their characteristics. Learn about the Hertzsprung-Russell diagram and the evolution of stars.

jcassady
Download Presentation

Supernova Explosions and Cosmic Ray Sources in Our Galaxy

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Истина проходит через три стадии: сначала ее высмеивают, потом ей яростно сопротивляются, и, наконец, принимают ее как очевидную. Артур Шопенгауер About cosmic ray sources Y. Stozhkov, Lebedev Physical Institute, RAS, Moscow, Russia ICPPA-20172-5 October 2017 Moscow

  2. Now it is accepted that supernova explosions are the main sources of cosmic rays in our Galaxy. These sources accelerate galactic protons up to energies ~1016 eV. In Galaxy supernovae of the second type blow up one time per ~(30-50) years and supernovae of first type - one time per (100-200) years. The last time the supernova explosion (Cassiopeia-A) was observed in 1750. The Table 1 gives some information about supernova explosions in Galaxy. Table 1. Supernovae explosions in Galaxy.For the last ~250 years we have to record about 8 supernova explosions.In our Galaxy there are many types of different stellar objects and some of them could produce cosmic ray. Let us consider this question.

  3. The Hertzsprung–Russell (HR) diagram is a scatter plot of stars showing the relationship between the stars' absolute magnitudes or luminosities versus their stellar classifications or effective temperatures. The diagram was created circa 1910 by Ejnar Hertzsprung and Henry Norris Russell and represents a major step towards an understanding of stellar evolution or "the way in which stars undergo sequences of dynamic and radical changes over time”. Most of the stars occupy the region in the diagram along the line called the main sequence. During the stage of their lives in which stars are found on the main sequence line, they are fusing hydrogen in their cores.

  4. In our Galaxy there are ~ 41011 stars similar to the Sun. About 90 % stars in Galaxy lie along the main sequence curve. We will consider the dwarf stars – the stars in the right bottom part of HR diagram, so called dwarf stars. The dwarf stars belong to G-M classes.Their main characteristics are:Temperatures – (6000  2500) К(for example, red dwarfAU Mic is at the distance r= 10 pc from the Sun, its temperature isabout Т= 4103 К);Mass is – (1  0.06) М๏;Radii – (1  0.1) R๏;Luminosities – (2 0.0008) L๏(L๏ = 3.86 1033erg/s);The density of flare dwarf stars in Galaxy equal to ~0.056 stars/pc3. The total star density is in 2 times higher (~0.133stars/pc3 );(Р.Е. Гершберг «Активность солнечного типа звезд главной последовательности», изд-во Астропринт, Одесса, 2002 г., 688 стр.)

  5. The energy density of cosmic rays in our Galaxy is wCR (0.3 - 1 ) eV/сm3.The energy density of electrons is wе 3103 eV/сm3. The total energy of cosmic rays in Galactic disk is evaluated as WCR 1054erg. What does the distance of cosmic rays come to us from? R=[2D(E)t]0.5; D(E) – diffusion coefficient, D(E) = 1028E cm2/s, where =(0.3-0.7), [E]=GeV. For t =108 years and E = 1.0 GeV we have R  2.6 kpc, For t =108 years and E = 10 GeV we have R  8.2 kpc, For t =108 years and E = 1.0 TeV we have R  14.6 kpc. Flashing stars radiate H and other emission lines and they give powerful X-ray radiation.In the range of (1-8 Å) our Sun radiatesX-rays and the ratio of (Lx/Lbol)  109, where Lx and Lbol are the luminosity in X-rays and bolometric one.For red dwarfs this ratio equals to (Lx/Lbol)  106. The most active red dwarfs have <Lx >  1030 erg/s. In solar activity minimum our Sun has <Lx๏>  21026 erg/s and in solar activity maximum <Lx๏>  51029 erg/s. Red dwarfs have more powerful stellar wind in comparison with solar one. Our Sun lose ~ (10-14 - 10-15) M๏/year, red dwarfs lose ~ (10-11 - 10-12) M/year.

  6. Our Sun and red dwarfs have spots (sunspots and stellar spots accordingly). The last were discovered in 1959. The total square of sunspots is less than 0.5% of total solar surface. On the of red dwarfs stellar spots cover from ~10% up to ~90% of stellar surface. The cyclic in the stellar spot changes is observed.The bolometric deficit of red dwarf radiation  = [(Tphot)4– (Tspot)4]/ (Tphot)4runs up ~ 30 %.The number of stellar spots and flare activity on red dwarfs exceed the solar ones in several orders. Magnetic field on these stars can amount to ~20 kG. On the Sun it is about 2 kG. Solar flares have the duration from several minutes up to several hours and the total energy of the optical radiation comes to ~ (1026 - 1031) erg.During flares on red dwarfs the optical luminosity of the star increases in several times. The total energy in optical range grows up to ~ 1035 erg. The duration of stellar flares equals to from the parts of second up to tens of hours.

  7. Now more than 1200 flashing stars were recorded with number flares more than 4000. On red dwarf star UV Getthe stellar flare occurs ~every hour. UV Gethas the following characteristics: r = 2.7 pc, there are stellar spots, (RUV/R๏)  0.16, (MUV/M๏)  0.1, log LUV 30.91. Solar flare activity is in 104 times lower than flare stellar activity of very active red dwarfs. The total energy of most powerful solar flares is evaluated as several units1032erg. The total energy of most powerful stellar flares can get 31036 erg. Magnetic fields on the Sun are concentrated in magnetic tubes (B ~ 1-2 kG) and in active regions (B ~ 1-3 kG), on active red dwarfs they are about B~20 kG. Thus, it is difficult to imagine that stellar flares on active red dwarf stars do not produce cosmic rays. Let us consider the question: could stellar flares on active red stars provide the density of cosmic ray energy in our Galaxy?

  8. In the Galaxy this value is wH wGwCR  0.5 eV/сm3. The total energy of cosmic rays in the Galaxy equal to WCR= wCRVG 1054erg, whereVG = 51066 сm3 – the volume of Galactic disk. WCR= Р1sourcenCR, where P1 is the power of 1 source,  = 108years is lifetime of cosmic ray particles in our Galaxy, nCR is the number of active red dwarfs. The average power of one stellar flare on active red dwarf is ~1035 erg and power stellar flares take place one per week. ThenР1  1037erg/year. The number of active red dwarfs is nCR= kN = 21010 , where N = 41011 is the number of stars in Galaxy, k = 0.1is the coefficient showing the part of active dwarfs in the total number of stars in our Galaxy. We need to take into account that only 10% of the total stellar flare energy expands for cosmic rays. Then we will have WCR= 0.1Р1nCR0.1(1037erg/year)(108years)(21010 )  1054erg. This value is comparable with the estimation given above.

  9. The close cosmic ray sources can explain several experimental results. One of them is (1) the complex forms of proton, helium, electron and positron spectra, obtained in PAMELA and AMS-02 experiments, (2) the increase of the ratio of positron flux to lepton one with the growth of energy, (3) the existence of anomaly component in cosmic rays observed in low energy range (from ~10 Mev/nucleon to ~70 MeV/nucleon).Let us discuss the exponents of spectra of electrons, positrons, protons and alfa-particles. After that we consider the dependence of ratio of positron flux to lepton one versus of particle energy.The spectral indices of the electron flux γe− and of the positron flux γe+ as a function of energy have complex form.Also, it concerns proton and helium spectra.

  10. The latest AMS data on the electron and positron fluxes, multiplied (for display purposes) by E3, where E is the electron or positron energy. The electron results (blue, left axis) are based on 16.5 million events and the positron results (red, right axis) are based on 1.1 million events [10]. e+ e-

  11. The spectral indices of the electron flux γe− and of the positron flux γe+ as a function of energy. The shaded regions indicate the 68% C.L. intervals including the correlation between neighboring points due to the sliding energy window.

  12. P He

  13. J(R) = AR- (PAMELA data) Protons Helium 30 – 80 GV 30 – 80 GV p = 2.801  0.007(stat)  0.002(syst) He = 2.71  0.01  0.002 80 – 230 GV80 – 240 GV p = 2.850  0.015  0.004 He = 2.766  0.01  0.027 > 232 GV> 243 GV p = 2.67  0.03  0.05 He = 2.477  0.06  0.03 R > 80 GV – 99.7% R > 80 GV – 95%

  14. Cosmic ray spectra from supernova explosion are N(Е) = A/E, where где CR 2.2, e- 2.2. These particles are in our Galaxy during ~ 108years and we observe CR= 2.7 with ΔCR 0.5, for electrons we have e- 3.2 and Δe- 1. Positron and electron spectra produced in the interactions of cosmic ray with galactic gas during cosmic ray lifetime in the Galaxy haveе+e- 2.7. Taking into account for positrons Δe+ 1, positron spectrum will have e+ 3.7. Thus, the ratio of positron flux to the sum of electrons and positrons will decrease with the growth of energy.

  15. Positron to Electron Fraction Secondary production Moskalenko & Strong 98 Adriani et al, Astropart. Phys. 34 (2010) 1 arXiv:1001.3522 [astro-ph.HE]

  16. F(Е) = [1 + m·exp(-k(E – E0))]1 - probability of e- and e+ release from the site of stellar flare. F(E) for 3 cases:  =  0.3,  = 0 and = 0.3. The value of is the difference of exponents for positron and electron spectra. For =  0.3 constants k, m andE0arem = 0.25, k = 0.04 andE0 = 90 GeV; for = 0 m = 0.05, k = 0.07 andE0 = 90 GeV; for = 0.3 m = 0.3, k = 0.05 andE0 = 90 GeV.

  17. Thank you for your attention

More Related